Two issues:

if you called begin or begingRepeating while still in waiting queue, it would create circular state (code did not set state to waiting)

If you called begin on one in active list, it would first remove it from list, but did not update the timings for items left as the timing all rely on items before it

When the run time issue adds an item back in to the list, it adds the item at the appropriate time, however it does not decrease the time of the item after where it was to take in account how much time the new item will take before we that next item starts to process it's _ms time

end() never disables interrupts

attention, patch for KINETISK only

https://forum.pjrc.com/threads/44904-Teensyduino-1-37-Beta-3?p=146286&viewfull=1#post146286

https://forum.pjrc.com/threads/44596-Teensyduino-1-37-Beta-2-(Arduino-1-8-3-support)?p=145141&viewfull=1#post145141

Fix for GCC generating bad code for DMAChannel TCD access when it can…

Fix some Warnings

fix warning: comparison of unsigned expression < 0 is always false

fix warning: comparison is always false due to limited range of data …

- unused parameter
- singed compare in int nvic_execution_priority(void)

analogWrite() can fail with LTO. Fix casts with undefined behavior.